本文学习自狄泰软件学院 唐佐林老师的 C语言进阶课程，图片全部来源于课程PPT，仅用于个人学习记录

实验-#errer的使用

#include <stdio.h>

#ifndef __cplusplus
    #error This file should be processed with C++ compiler.
#endif

class CppClass
{
private:
    int m_value;
public:
    CppClass()
    {

    }

    ~CppClass()
    {
    }
};

int main()
{
    return 0;
}
#error This file should be processed with C++ compiler.
/*output:

*/

实验-缺少#error

#include <stdio.h>

void f()
{
#if ( PRODUCT == 1 )
    printf("This is a low level product!\n");
#elif ( PRODUCT == 2 )
    printf("This is a middle level product!\n");
#elif ( PRODUCT == 3 )
    printf("This is a high level product!\n");
#endif
}

int main()
{
    f();

    printf("1. Query Information.\n");
    printf("2. Record Information.\n");
    printf("3. Delete Information.\n");

#if ( PRODUCT == 1 )
    printf("4. Exit.\n");
#elif ( PRODUCT == 2 )
    printf("4. High Level Query.\n");
    printf("5. Exit.\n");
#elif ( PRODUCT == 3 )
    printf("4. High Level Query.\n");
    printf("5. Mannul Service.\n");
    printf("6. Exit.\n");
#endif

    return 0;
}
/*output:
1. Query Information.
2. Record Information.
3. Delete Information.
*/

实验-#line 1的使用

#include <stdio.h>


int main()
{
    printf("%s : %d\n", __FILE__, __LINE__);//文件名 所在行号//129
    #line 1 "delphi_tang.c"//重新定义行号:下一行为1 文件名"delphi_tang.c"
								
    printf("%s : %d\n", __FILE__, __LINE__);//文件名 所在行号

    return 0;
}

/*output:
D:\Users\cy\Test\test1.c : 129
delphi_tang.c : 2
*/

实验-#line 1用于标记代码

#line 1用于标记代码编写人和行号(便于Debug),代码示例:

#include <stdio.h>

// The code section is written by A.
// Begin
#line 1 "a.c"

// End

// The code section is written by B.
// Begin
#line 1 "b.c"

// End

// The code section is written by Delphi.
// Begin
#line 1 "delphi_tang.c"


int main()
{
    printf("%s : %d\n", __FILE__, __LINE__);

    printf("%s : %d\n", __FILE__, __LINE__);

    return 0;
}

// End
/*output:
delphi_tang.c : 5
delphi_tang.c : 7
*/

小结

#error用于自定义一条编译错误信息

#warning用于自定义一条编译警告信息

#error和#warning常应用于条件编译的情形
#line用于强制指定新的行号和编译文件名